The present invention relates to an infrared detector element for detecting infrared rays by means of a pyroelectric material, and an infrared sensor unit and an infrared detecting device using the infrared detector element.
In recent years, a pyroelectric infrared sensor has been used in a microwave oven for measuring temperatures of foods to be cooked, in an air conditioner for controlling the room temperature, in an automatic door and a burglar alarm system for detecting people and the like utilizing the features of the pyroelectric infrared sensor to perform non-contact detection of the existence of an object and to carry out a non-contact measurement of temperatures, and its applications are considered to increase further from now on.
In general, an infrared sensor utilizes the pyroelectric effect of a pyroelectric element such as an LiTaO3 crystal and the like and electrical charges always appear on the surface of the pyroelectric element due to its spontaneous polarization. Under a stabilized condition of the pyroelectric material in the atmosphere, these electrical charges are coupled with electrical charges in the atmosphere to maintain a neutralized state electrically. When infrared rays are incident on the pyroelectric element, its temperature changes, thereby causing the electrical charges on the surface of the pyroelectric element to lose and change the electrically neutralized state. At this time, the electrical charges appearing on the surface of the pyroelectric element are detected by the infrared sensor, thereby measuring the amount of incident infrared rays. An object is generally radiating infrared rays in accordance with its temperature and the existence and temperature of the object can be detected by the use of the infrared sensor.
Next, a description is given to an infrared detector element that serves as a technical background of the present invention with reference to drawings.
FIG. 11(a) is a plan view of an infrared detector element that describes the background technology of the present invention and FIG. 11(b) is a cross-sectional view of the infrared detector element of FIG. 1(a).
In the drawing, a pyroelectric element 1 has a pair of rectangular first electrodes 2 and 3, each of which performs the function of an infrared absorbing film, formed on the surface thereof with electrical connections made in such a way that the electrodes 2 and 3 are opposite in polarity and also has a pair of second electrodes 4 and 5 of the same rectangular shape as the first electrodes 2 and 3, formed on the bottom surface thereof.
These first electrodes 2 and 3 and second electrodes 4 and 5 constitute, respectively, an infrared detecting segment. These two of the second electrodes 4 and 5 are opposite in polarity and connected in series or in parallel with each other. The spacing between the second electrodes 4 and 5 is usually made the same as the spacing between the infrared ray incident electrodes or larger than 0.8 mm, thereby building a dual element type infrared detector element that does not incur such an adverse effect as crosstalk.
This infrared detector element is finished by connecting the pyroelectric element 1 to a wiring board 7 by means of a pyroelectric element support 6, while keeping the infrared detecting segment in a thermally insulated state.
When the infrared detector element as structured above is used, an optical system with a Fresnel lens and the like is employed, thereby projecting a plurality of configurations of the infrared detector element in a detection area to create a detecting domain. At this time, when an object to be detected such as people and the like, for example, moves in the direction crossing the infrared detecting segment (in the X direction), a xe2x80x9cminus outputxe2x80x9d is generated immediately after a xe2x80x9cplus outputxe2x80x9d, thus gaining a maximum output extending from xe2x80x9cpeak to peakxe2x80x9d. On the other hand, when an object to be detected moves in parallel to the infrared detecting segment (in the Y direction), the xe2x80x9cplus outputxe2x80x9d and xe2x80x9cminus outputxe2x80x9d are generated simultaneously, thus ending up with gaining no output due to a canceling effect.
The Japanese Patent Unexamined Publication TOKKAIHEI-2-201228 discloses an infrared detector element with an infrared detecting segment shaped like a right triangle.
In this case, an output can be obtained in both X and Y directions but, when an object to be detected moves in a 45xc2x0 direction, the xe2x80x9cplus outputxe2x80x9d and xe2x80x9cminus outputxe2x80x9d are generated simultaneously in the same way as experienced with the foregoing infrared detector element with a rectangular type infrared detecting segment, resulting in no output due to a canceling effect.
As described in the above, since an infrared detector element is used with home appliances such as a lighting fixture, an air conditioner and the like, the infrared detector element is required to be nondirectional against an object to be detected in whatever directions it may move.
The object of the present invention is to provide an omnidirectional infrared detector element that responds with an output against an object to be detected in whatever directions it may move.
In order to accomplish the object as described in the above, the present invention discloses a setup comprising:
a pyroelectric material; and
a pair of infrared detecting segments, which are close to trapezoidal in shape, respectively, and disposed on the pyroelectric material with electrical connections made in such a way that the infrared detecting segments are opposite to each other in polarity, in which the upper side of the close to trapezoidal shape of one of the infrared detecting segments is aligned in the same direction as the lower side of the close to trapezoidal shape of the other infrared detecting segment.
The present invention also discloses a setup comprising:
an infrared detecting segment disposed on a pyroelectric material in such a way that the upper side of one of the close to trapezoidal shapes is aligned in the same direction as the other close to trapezoidal shape; and
a wiring board electrically connected to the infrared detecting segment via a pyroelectric material holder.
The present invention also discloses a setup comprising:
a mounting base provided with lead electrodes;
an infrared detector element including a pyroelectric material disposed on the mounting base and a pair of infrared detecting segments formed on the pyroelectric material in such a way that the upper side of one of the close to trapezoidal shapes is aligned in the same direction with the lower side of the other close to trapezoidal shape or the longer side of one of the close to triangular shapes is opposing to the longer side of the other close to triangular shape, further with electrical connections made in such a way that the pair of infrared detecting segments are opposite to each other in polarity;
a cylindrical encapsulating member surrounding at least the infrared detector element;
an infrared ray incident window covering an opening of the encapsulating member; and
a lens array located apart upward from the infrared ray incident window and formed of a plurality of diffraction type optical elements, the lens array having a focal length extending to as far as the vicinity of the infrared detecting element.
The present invention also discloses a setup comprising:
mounting base provided with lead electrodes;
an infrared detector element including a pyroelectric material disposed on the mounting base and a pair of infrared detecting segments formed on the pyroelectric material in such a way that the upper side of one of the close to trapezoidal shapes is aligned in the same direction as the lower side of the other close to trapezoidal shape or the longer side of one of the close to triangular shapes is opposing to the longer side of the other close to triangular shape, with electrical connections made in such a way that the pair of the infrared detecting segments are opposite to each other in polarity;
a cylindrical encapsulating member surrounding at least the infrared detecting element; and
an infrared ray incident window lens array located to cover an opening of the encapsulating member and formed of a plurality of diffraction type optical elements with a focal length thereof extending to as far as the vicinity of the infrared detecting element.
With the foregoing setups realized by the present invention, from whatever directions an object to be detected may make an intrusion, respective areas of the infrared detecting segment traversed by the object to be detected are not the same with one another, thereby allowing an output to be generated without cancellation even when two outputs different from each other in polarity are generated simultaneously.